Electroosmosis is widely observed in different micro-scale flows. Flow modification due to electroosmosis is important for applications related to fuel cells such as micro direct methanol fuel cells and micro-scale devices. Mechanism for delivering methanol into the micro-fuel cell is very important process affecting its power density and often they need to be stand alone systems with no external pumps or other ancillary devices to eliminate the parasitic power loss accounting from fuel feed. In this study, numerical simulation has been carried out for the electroosmotic effect on pressure-driven flows in a serpentine microchannel whose side walls are subjected to variable zeta potentials. It is observed that for a non-uniform zeta potential, the secondary vortex pair and their strength of motion generated by electroosmosis is modified asymmetrically, corresponding to the degree of the variation in and the magnitude of the zeta potential. It is also found that the flow profiles are quite different for variable zeta potentials as compared to a constant zeta potential applied on the channel walls. The flow phenomena at the bend of the serpentine channel has also been investigated, and flow control is possible by regulating the applied zeta potential on the channel walls. It is observed that vortices shift in a clockwise direction as the applied zeta potential is increased on the walls of the serpentine channel. Formation of additional vortices has also been observed for very low values of applied zeta potential. (c) 2006 Elsevier B.V. All rights reserved.